1. Field of the Invention
The present invention relates to a method of producing 2,2-bis(3-nitro-4-hydroxyphenyl)hexafluoropropane which is usable as an intermediate material for 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane or the like.
2. Description of the Prior Art
In order to produce 2,2-bis(3-nitro-4-hydroxyphenyl)hexafluoropropane, two methods have been widely used, one being a method in which, as is shown in Japanese Patent First Provisional Publication No. 59-109546, 2,2-bis(4-hydroxyphenyl)hexafluoropropane is mixed with potassium nitrate in trifluoro acetic acid, and the other being a method in which, as is shown in J.POLYMER SCIENCE, POLYMER CHEM. ED. 20,2381 (1982), 2.2-bis(4-hydroxyphenyl)hexafluoropropane is mixed with trifluoromethane sulfonic acid to form triflate (trifluoromethanesulfonate) and then the triflate is nitrated by mixed acid.
However, in these conventional methods, usage of expensive solvents and agents is needed. Furthermore, purification of product should be effected by means of troublesome distillation.
Furthermore, according to J.Polymer Science, Polymer Lett., 7,185 (1969) in which nitration on 2,2-bis(4-hydroxyphenyl)propane is discussed, it is reported that when 2,2-bis(4-hydroxyphenyl)propane was nitrated by concentrated nitric acid in mixed solvent of benzene-acetic acid, about 38% dinitro-substance was obtained, but, the dinitro-substance exhibited poor purity due to contamination by mononitro-substance and trinitro-substance. The report concluded that preferably, nitration of dichloroformate of 2,2-bis(4-hydroxyphenyl)propane should be made by silver nitrate in acetonitrile. In either case, it is difficult to obtain a highly purified dinitro-substance when using nitric acid.